Dermatomyositis is a non-infectious inflammation of muscle tissue and skin.
Dermatomyositis and its sister disease, polymyositis, belong to a large category of connective tissue disorders that include lupus erythematosus, rheumatoid arthritis, and scleroderma (systemic sclerosis). They are all believed to represent “autoimmune disorders,” wherein the body launches an attack against its own tissues. These chronic, progressive conditions lead to tissue destruction. They are potentially serious conditions that require care from your doctor. The sooner these disorders are treated, the more favorable the outcome. If you suspect you have dermatomyositis, contact your doctor immediately.
Causes
Although the cause or causes are not known, a viral infection may trigger the onset of dermatomyositis by causing the body’s immune system to misidentify infected skin and muscle tissue as a threat.
Risk Factors
The following factor increases your chance of developing dermatomyositis:
Symptoms
If you experience any of these symptoms, do not assume it is due to dermatomyositis. These symptoms may be caused by other, less serious health conditions. If you experience any one of the following symptoms, see your physician.
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Weakness, especially of the hips and thighs, making it difficult to negotiate stairs and stand up, but also arms or neck
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Aching leg (arm or neck) pain
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Tender muscles
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Difficulty swallowing
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Violaceous (or heliotrope), bumpy, or scaly skin rash, especially around the eyes, upper back, elbows, or knuckles
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Itching
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Photosensitivity (skin burning or itching upon exposure to sunlight)
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Aching and color changes (red, white, and blue) in fingers, especially in cold temperatures
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Joint pain
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Shortness of breath
Diagnosis
Your doctor will ask about your symptoms and medical history, and perform a physical exam. You are likely to be referred to a rheumatologist (a doctor who specializes in musculoskeletal disorders).
Tests may include the following:
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Blood tests
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Electromyogram (EMG)–to test the electrical responsiveness of your muscles. This test involves inserting tiny needles into affected muscles and stimulating them with tiny electrical currents.
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Muscle Biopsy–surgical removal of a small piece of muscle to examine it under a microscope
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Margnetic Resonance Imaging (MRI) or ultrasound to help detect inflammation in your muscles. An MRI is a test that uses magnetic waves to make pictures of structures inside the body. An ultrasound is a test that uses sound waves to examine parts of the body.
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Skin Biopsy–surgical removal of a small piece of skin to examine it under a microscope
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Cancer Tests–in adults, dermatomyositis is associated with cancer about 15% of the time and may be the first sign of cancer
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CAT Scan (CT)–a type of x-ray that uses a computer to make pictures of structures inside of the body, in this case the chest, since dermatomyositis may be associated with lung disease
Treatment
Talk with your doctor about the best treatment plan for you. Treatment options include the following:
General Health Maintenance
Because dermatomyositis is a serious disease with long-term implications, physical exercise, a healthy lifestyle, and a nutritious diet are an integral part of treatment.
Cortisone
Cortisone-like drugs, usually oral prednisone, often produce a satisfactory response over the course of 2-3 months, after which the dose may be reduced according to the activity of the disease.
Immunosuppressive Drugs
Agents used to treat cancer and organ transplants such as methotrexate, cyclophosphamide, chlorambucil, azathioprine, mycophenolate mofetil, and cyclosporine have helped patients who did not respond to prednisone.
Experimental Treatments
Intravenous immune globulin, total body irradiation, plasma exchange, and leukapheresis have been used for severe disease.
Prevention
There are no known ways to prevent dermatomyositis.
RESOURCES:
American Academy of Family Physicians
http://www.aafp.org
Muscular Dystrophy Association
http://www.mdausa.org
The Myositis Association
http://www.myositis.org
National Institute of Neurological Disorders and Stroke
http://www.ninds.nih.gov
CANADIAN RESOUCRES:
The Arthritis Society
http://www.arthritis.ca
Muscular Dystrophy Canada
http://www.muscle.ca
References:
Berkow R, Beers MH, Burs M, eds. The Merck Manual, 17th ed. West Point, Pa: Merck & Co; 1999.
Bolognia JL, Jorizzo J, Rapini RP. Dermatology. London: Elsevier Science; 2003.
Dalakas MC. Polymyositis, dermatomyositis, and inclusion body myositis. In: Kasper DL, et al, eds. Harrison's Principles of Internal Medicine, 16th ed. New York: McGraw-Hill; 2005: 2540-2545.
Dermatomyositis. DynaMed website. Available at: http://www.dynamicmedical.com/dynamed.nsf?opendatabase. Accessed August 2005.
Wong EH, Hui AC, Griffith JF,et al. MRI in biopsy-negative dermatomyositis. Neurology. 2005 Feb 22;64(4):750.
